Apparatus and method for thermal stabilization of PCB-mounted electronic components within an enclosed housing

ABSTRACT

An apparatus comprises a matrix of thermoelectric devices for applying thermal gradients across an electronic component mounted in a PCB substrate within an enclosed housing. A matrix of thermosensitive devices are placed around the perimeter of the electronic component to measure thermal gradients associated with the component. A controller controls the matrix of thermoelectric devices based on the thermal gradients measured by the matrix of thermosensitive devices with a matrix of thermocouple coefficients.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 60/839,515, filed Aug. 22, 2006, which is incorporated herein byreference in its entirety.

BRIEF DESCRIPTION OF THE INVENTION

This invention relates generally to stabilizing the temperature ofelectronic components. More particularly, this invention is directedtowards using a control processor for stabilizing thermal gradientsacross an electronic component that is PCB-mounted within an enclosedhousing.

BACKGROUND OF THE INVENTION

Electronic components mounted on Printed Circuit Boards (“PCBs”) arepervasive throughout a wide range of consumer and industrial products.With recent advances in semiconductor technologies, these electroniccomponents have become smaller, faster, and more powerful. They havealso become more densely packed in the PCBs, which may include manylayers of intricate electrical circuits and connections supporting thecomponents. This miniaturization has led to several new challenges inelectronic component and PCB design, including the ability to controlthe heat generated by the electronic components during their operation.

A considerable amount of heat may be generated by electronic componentsduring their operation, including transistors, integrated circuits,power controls, switches, oscillators, microprocessors, and the like.The heat generated may cause component failure or malfunction if notproperly controlled. Certain types of electronic components may beparticularly susceptible to heat dissipation or other temperatureeffects. In some cases, the temperature must be stabilized for thecomponents to remain within their operating range.

For example, voltage-controlled crystal oscillators (“VCXOs”) oroven-controlled crystal oscillators (“OCXOs”), are highly sensitive totemperature gradients, both in time and across their physicaldimensions. These temperature gradients may result in undesirable outputfluctuations such as thermally induced frequency drift. These outputfluctuations may in turn impact the quality of real-time applicationsand services in computer networks where these oscillators are heavilyused, including Pseudo-Wire Emulation (“PWE”), Voice over IP (“VoIP”),video conferencing, and streaming services.

Conventional approaches to control or stabilize the temperature in a PCBinclude the use of heat sinks and temperature compensation circuitsmounted on or external to the PCB, as well as thermally-insulatedenclosures to house the PCB. For example, heat sinks are typicallymounted on the active surface of a semiconductor die to absorb heat fromthe die and dissipate the heat by convection into the cooler air,thereby maintaining the temperature across the PCB.

Additional temperature control may be provided by temperaturecompensation circuits which generally stabilize the performance of agiven electronic component or PCB across a wide range of temperatures.In the case of VCXOs and OCXOs, temperature compensation circuits mayprovide a relatively flat frequency output over a wide range ortemperatures.

The PCB and temperature compensation circuits may be enclosed within athermally-insulated enclosure or housing to protect the PCB andelectronic components therein from outside environment hazards, such asambient heat, moisture, dust, debris, and so on. Thermally-insulatedhousings may also be used to prevent electromagnetic signals generatedby the electronic components from causing Electromagnetic Interference(“EMI”) or Radio Frequency Interference (“RFI”) to other devices intheir vicinity and vice-versa.

The thermally-insulated housings may also include temperature sensors tomonitor the temperature around electronic components within thehousings. In cases where temperature stability is desired for optimalperformance, one or more heating elements may be used together with thesensors to maintain a given temperature gradient across a component.Based on the temperature measured by the sensors, the heating elementsmay generate more or less heat to achieve the desired temperaturegradient.

For example, a single planar heating element has been used to thermallystabilize electronic components mounted on a PCB within athermally-insulated housing. Though a single planar heating element maystabilize time-based thermal fluctuations for a given electroniccomponent, it may not compensate for thermal gradients across thephysical dimensions of the component. These thermal gradients aredependent on the relative positions of other heat-generating electroniccomponents on the PCB, such as power supplies.

A set of linear heating elements that are closely spaced and in parallelmay also be used. Although a set of linear heating elements may providesome capability to vary the heating across the physical dimensions ofthe component, the set may be insufficient to eliminate outputfluctuations that degrade real-time applications and services, such asin the case of VCXOs and OCXOs that must maintain a flat frequencyoutput over a wide range of temperatures.

Accordingly, it would be desirable to provide a thermal-managementapproach that can effectively stabilize temperature gradients across anelectronic component mounted on a PCB across both time and the physicaldimensions of the component.

SUMMARY OF THE INVENTION

An apparatus, controller and method are described to stabilize thetemperature across an electronic component. One embodiment of theinvention includes an apparatus having a matrix of thermoelectricdevices to set thermal gradients across the electronic component, amatrix of thermosensitive devices to measure thermal gradientsassociated with the electronic component and a controller forcontrolling the matrix of thermoelectric devices based on the thermalgradients measured by the matrix of thermosensitive devices with amatrix of thermocouple coefficients.

Another embodiment of the invention includes a controller withexecutable instructions to detect thermal gradients measured by a matrixof thermosensitive devices associated with an electronic component andto control a set of current values applied to a matrix of thermoelectricdevices based on the detected thermal gradients and with a matrix ofthermocouple coefficients.

A further embodiment of the invention includes a method for stabilizingthe temperature of an electronic component mounted in a printed circuitboard substrate within an enclosed housing. The electronic component isheated with a matrix of thermoelectric devices arranged in a firstsurface of the substrate opposite to a second surface of the substratemounting the electronic component. Thermal gradients surrounding theelectronic component are measured with a matrix of thermosensitivedevices mounted on the second surface of the substrate. The heat appliedby the matrix of thermoelectric devices is controlled on the thermalgradients measured by the matrix of thermosensitive devices.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is more fully appreciated in connection with the followingdetailed description taken in conjunction with the accompanyingdrawings, in which like reference characters refer to like partsthroughout, and in which:

FIG. 1 illustrates a schematic diagram of an apparatus for thermalstabilization of an electronic component constructed according to anembodiment of the invention;

FIG. 2 illustrates a side view of an apparatus for thermal stabilizationof an electronic component constructed according to an embodiment of theinvention;

FIG. 3 illustrates a top view of an apparatus for thermal stabilizationof an electronic component constructed according to an embodiment of theinvention;

FIG. 4 illustrates a bottom view of an apparatus for thermalstabilization of an electronic component constructed according to anembodiment of the invention; and

FIG. 5 illustrates a circuit diagram for one exemplary embodiment of thethermoelectric devices shown in FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

An apparatus, controller, and method for stabilizing the temperatureacross an electronic component are provided. As generally used herein,an electronic component may be any electronic element packaged in adiscrete form with two or more connecting leads or pads. Electroniccomponents may be packaged singly, such as resistors, capacitors, andtransistors, or in groups, such as in amplifiers, oscillators, andintegrated circuits, among others. The electronic components may betypically mounted on Printed Circuit Boards (“PCBs”), which are used tomechanically support or electrically connect electronic components usingconductive pathways or traces etched onto a non-conductive substrate. Inaccordance with the invention, the electronic components may bethrough-hole or surface mounted. Also in accordance with the invention,a PCB may be placed inside an enclosed volume or housing.

A schematic diagram of an apparatus for thermal stabilization of anelectronic component constructed according to an embodiment of theinvention is illustrated in FIG. 1. Apparatus 100 is designed tostabilize the temperature around and across electronic component 105mounted on multi-layer PCB substrate 110. Electronic component 105 isenclosed in thermally-stabilized housing 115, described in more detailherein below. It is appreciated that electronic component 105 may bethrough-hole or surface mounted on the surface of PCB substrate 110.

Temperature stabilization is achieved with a matrix of thermoelectricdevices including a plurality of thermoelectric devices 120 a-m, amatrix of thermosensitive devices including a plurality ofthermosensitive devices 125 a-n, and a controller 130. As generally usedherein, a matrix of devices refers to a plurality of devices arranged ina two-dimensional pattern or grid. The matrix of devices may alsoinclude devices that are outside the two-dimensional grid, such as, forexample, thermosensitive device 125 n.

The matrix of thermoelectric devices 120 a-m may be arranged in atwo-dimensional grid on a surface of PCB substrate 110 opposite theelectronic component 105, such as, for example, on the surface under theelectronic component 105. The matrix of thermosensitive devices 125 a-nmay be arranged in a two-dimensional grid on a surface of PCB substrate110 surrounding the perimeter of and on the same side as the electroniccomponent 105. Some or all of thermosensitive devices 125 a-n may alsobe in direct contact with electronic component 105, such as, forexample, mounted on a surface of electronic component 105. In addition,one or more thermosensitive devices may be external to thethermally-stabilized housing 115 to measure thermal gradients associatedwith the PCB substrate 110 and the external ambient, such asthermosensitive device 125 n.

Controller 130 is used to control the plurality of thermoelectricdevices 120 a-m. Controller 130 generates a set of current values forthe plurality of thermoelectric devices 120 a-m. The plurality ofthermoelectric devices 120 a-m convert the set of current values intothermal gradients that are applied across the electronic component 105.It is appreciated that controller 130 may be within or external to thethermally-stabilized housing 115.

The thermal gradients can be used to heat or cool the electroniccomponent 105. In one exemplary embodiment, the plurality ofthermoelectric devices 120 a-m may be a plurality of heating devices toheat the electronic component 105. For example, a plurality of heatingdevices may be used to heat a crystal oscillator and maintain a constanttemperature across the oscillator and within the thermally-stabilizedhousing 115. In another exemplary embodiment, the plurality ofthermoelectric devices 120 a-m may be a plurality of cooling devices forcooling down electronic component 105 and preventing heat dissipationaround the component 105.

In another exemplary embodiment, the plurality of thermoelectric devices120 a-m may be hybrid heating and cooling devices, such as, for example,Peltier thermoelectric devices. It is appreciated that any combinationof heating and cooling devices may be used in the matrix ofthermoelectric devices 120 a-m.

The set of current values applied to the plurality of thermoelectricdevices 120 a-m are generated by the controller 130 based on thermalgradients measured by the plurality of thermosensitive devices 125 a-n.The thermosensitive devices 125 a-n may be arranged in a two-dimensionalgrid to detect the thermal gradients on the component side of the PCBsubstrate 110. The controller 130 receives the thermal gradients fromthe thermosensitive devices 125 a-n and generates a set of currentvalues for the thermoelectric devices 120 a-m to convert into a set ofthermal gradients applied across the electronic component 105. The setof current values are generated to maintain a desired temperatureset-point across the electronic component 105 and within thethermally-stabilized housing 115.

In one exemplary embodiment, controller 130 is a Multiple-Input,Multiple-Output (“MIMO”) controller. The MIMO controller maintains amatrix of thermocouple coefficients {circle around (−)}_(ij), which aremeasured in ° C. mm²/Watt. Each thermocouple coefficient {circle around(−)}_(ij) is expressed as {circle around (−)}_(ij)=T_(j)/V_(i), whereT_(j) represents a thermal gradient detected by thermosensitive device jand V_(i) represents a voltage per area applied to thermoelectric devicei. With M thermoelectric devices and N thermosensitive devices, thematrix of thermocouple coefficients is a M×N matrix.

In one exemplary embodiment, a symmetric placement of thermoelectricdevices 120 a-m in relation to thermosensitive devices 125 a-n yields asymmetric MIMO feedback matrix composed of the {circle around (−)}_(ij)coefficients. This reduces the complexity of the MIMO controller 130.Further, an equal number, N, of thermosensitive devices andthermoelectric devices ensures a square N×N feedback matrix and reducesthe complexity of the MIMO controller 130.

It is appreciated that one or more of the thermosensitive devices 125a-n may be a thermosensitive device external to the thermally-stabilizedhousing 115 to measure thermal gradients associated with the PCBsubstrate 110 and the external ambient, such as thermosensitive device125 n. Accordingly the matrix of thermocouple coefficients may includeparasitic impedance coefficients associated with the one or moreexternal thermosensitive devices, such as external thermosensitivedevice 125 n.

The thermocouple coefficients in the matrix are generated to maintain adesired temperature set-point across the electronic component 105 andwithin the thermally-stabilized housing 115. In one exemplaryembodiment, the desired temperature set-point may be initially set at anambient temperature value of 65° F. The thermocouple coefficients maybe, in turn, initially set to achieve the initial temperature set-pointacross the electronic component 105. Accordingly, the thermocouplecoefficients are in general kept constant to achieve the desiredtemperature set-point.

The desired temperature set-point may be adjusted over time as theplurality of thermosensitive devices 125 a-n detects different thermalgradients around the electronic component 105. The desired temperatureset-point may be adjusted, for example, based on the average thermalgradients detected by the plurality of thermosensitive devices 125 a-nmeasured over a 24-hour period. The thermocouple coefficients may beadjusted accordingly.

In one exemplary embodiment, the desired temperature set-point may beset at a value above the average thermal gradients detected in the past24-hour period, such as, for example, at 25° F. degrees above theaverage. This provides a sufficient margin to ensure a stabilizedtemperature within the housing in cases where the temperature suddenlyfluctuates between extremes in any given time period. This also ensuresthat the desired set-point will remain above the average thermalgradients at any given time.

It is appreciated that the desired temperature set-point may be adjusteddifferently, such as, for example, by setting it to be at or below theaverage thermal gradients detected in the past 24-hour period. Further,it is also appreciated that the desired temperature set-point may bemaintained constant unless the temperature associated with the PCBsubstrate 110 and the ambient temperature exceed some pre-determinedtemperature bounds.

In addition, it is appreciated that the number of devices shown in FIG.1 is shown for illustration purposes only. For example, multipleelectronic components could be mounted on PCB substrate 110. In thiscase, each electronic component could have a set of thermoelectricdevices and a set of thermosensitive devices associated with it. Asingle or multiple controllers could be used to control the temperatureacross the electronic components.

A side view of an apparatus for thermal stabilization of an electroniccomponent constructed according to an embodiment of the invention isillustrated in FIG. 2. Apparatus 100 includes dual-chambered enclosure205 having upper metal housing 210 and lower metal housing 215 arrangedso as to surround an internal area of multi-layer PCB substrate 220.Electronic component 225 to be thermally stabilized is mounted onmulti-layer PCB substrate 220. Thermal conduction to the electroniccomponent 225 is achieved by use of thermal conducting tape or foam 230between the body of the electronic component 225 and the multi-layer PCBsubstrate 220.

It is appreciated that dual-chambered enclosure 205 may be amulti-chambered enclosure having more than two chambers. For example, amulti-chambered housing may include housings within housings separatedby insulative material.

In accordance with the invention, a matrix including a plurality ofthermoelectric devices 235 a-d is arranged in a two-dimensional grid ona surface of the multi-layer PCB substrate 220 opposite the electroniccomponent 225. A matrix including a plurality of thermosensitive devices240 a-b is also arranged in a two-dimensional grid around the perimeterof the electronic component 225 for detecting the temperature acrosselectronic component 225. The matrix also includes thermosensitivedevice 240 c mounted on the top surface of electronic component 225. Acontroller (not shown in FIG. 2) controls the current values applied tothe plurality of thermoelectric devices 235 a-d based on thermalgradients detected by the plurality of thermosensitive devices 240 a-c.

Dual-chambered enclosure 205 also includes a conductive shield 245surrounding the internal area of the multi-layer PCB substrate 220 inelectrical contact with the upper and lower housings 210-215. Inaddition, an EMI/RFI shield 250 fully encloses the area around theelectronic component 225. Upper and lower chambers 255 a-b are formed bycavities cast into the upper and lower metal housings 210-215. For eachhousing, a tight EMI seal is formed into the surface of the PCB 220 andaround the perimeter of the enclosed space by a metal-filled elastomeror polymer gasket material 260 that is contact to conductive shield 245on both surfaces of PCB 220.

The upper and lower housings 210-215 are kept in mechanical compressionto ensure good conductivity and shielding around the entire perimeter ofthe electronic component 225. Plated through vias 265 a-g are used tolink the conductive shield 245 to conductive shield traces on the innerlayers of PCB 220. The number and spacings of the vias and inner layerconductive shields are chosen to minimize EMI and RFI energy escaping orentering the upper and lower housings 210-215.

An insulative material fills the upper and lower chambers 255 a-b ofupper and lower housings 210-215. The insulative material may be, forexample, a high-density insulating Styrofoam. A plurality of openings270 a-b may also be disposed about in the PCB substrate 220 to interruptany conductive transfer of heat that may take place during operation ofthe electronic component 225.

It is appreciated that electrical power, ground and other signals areprovided to the enclosed area within the upper and lower housings210-215 through regions intermediate the plurality of openings 270 a-b.Power, ground and signal traces from the PCB 220 to the upper and lowerchambers 255 a-b may enter the chambers 255 a-b through any number ofisthmuses in PCB 220. In one exemplary embodiment, the power, ground andsignal traces may enter the chambers 255 a-b through a single isthmus(such as shown in FIG. 3) to localize heat dissipation through thetraces to one particular region. Further, the power, ground and signaltraces may be kept to a minimum to reduce the number of metal traceswhich are a major contributor to heat transfer between the upper andlower chambers 255 a-b to the PCB 220.

In one exemplary embodiment, all of the internally controllableelectronic components share a serial bus. In one embodiment, in additionto the power and ground traces, there may be additional signal tracesthat traverse the chambers' boundaries, such as, for example, a clocksignal, a serial data signal, and a serial clock for the serial bus. Theserial data signal may be used for the current values generated by thecontroller, such as controller 130 of FIG. 1.

It is appreciated that capacitive or inductive coupling may be used onthe signal paths to further reduce the number of traces. For example,the signal paths may be encoded with an 8 B/10 B encoding to remove theDC component when using capacitive coupling. In addition, opticaltransmission may be used to limit the signal traces and thus reduceparasitic heat loss.

A top view of apparatus 100 is illustrated in FIG. 3. Apparatus 100 isshown with a plurality of thermosensitive devices 240 a-h arranged in atwo-dimensional grid around the perimeter of electronic component 225and on the same surface of PCB 220 as electronic component 225.Thermosensitive devices 240 a-h are placed as close as possible toelectronic component 225 to monitor the temperature of a regionsurrounding the component 225.

It is appreciated that a multiplicity of thermosensitive devices may beused to measure thermal gradients around the component 225. As shown inFIG. 3, there are eight thermosensitive devices 240 a-i. It is alsoappreciated that one or more of thermosensitive devices 240 a-i may bein close thermal contact with electronic component 225. The one or morethermosensitive devices 240 a-i may also be in direct contact withelectronic component 225. For example, one or more thermosensitivedevices may be mounted on the surface of electronic component 225, suchas thermosensitive device 240 c (shown in FIG. 2) mounted on top ofelectronic component 225.

FIG. 3 also shows a set of void channels or perforations 270 a-h in thePCB 220 arranged around the perimeter of electronic component 225 andinternal to the EMI/RFI shield 250. Much of the heat leakage that occursfrom within the EMI/RFI shield 250 to the external environment takesplace through isthmuses 300 a-h of PCB 220 intermediate the voids 270a-h. The placement of voids 270 a-h reduces the heat conduction throughthe isthmuses 300 a-h. Strategic placement of thermoelectric devicesadjacent to the isthmuses 300 a-h serves to combat the temperaturegradients surrounding and across electronic component 225.

A set of thermoelectric devices adjacent to isthmuses 300 a-h isillustrated in FIG. 4. Thermoelectric devices 235 a-i are also arrangedin a two-dimensional grid but on a surface of PCB substrate 220 thatsurrounds and is opposite to the thermally stabilized region on theother side of PCB 220. The placement pattern for the thermoelectricdevices 235 a-i is intended for thermal dispersion in a given pattern,either uniform or not. There are nine thermoelectric devices 235 a-i asshown, with each one serving an area on the side opposite the electroniccomponent 225.

Metal-plate through vias may be dispersed on a metal surface to conductheat from the surface mounting the thermoelectric devices 235 a-i to thesurface mounting the electronic component 225. Each thermoelectricdevice surface area may be separated from other thermoelectric devicesto provide better separation of control in a given area. In oneexemplary embodiment, the thermally stabilized side surface area may bea single metal surface to disperse heat in a thermal dispersion patternto the electronic component 225, either uniformly or not.

A circuit diagram for a thermoelectric device constructed in accordancewith one embodiment of the invention is illustrated in FIG. 5.Thermoelectric device 500 is a heating device for heating an electroniccomponent as described above. Serial Digital Analog Converter (“SerialDAC”) 505 receives serial data representing a set of current values froma controller, such as controller 130, at its “SDA” input. A serial clocksignal is input into its “SCL” input and a supply voltage is input intothe “V” input. Serial DAC 505 converts the serial data sent from thecontroller into a voltage output at “DOUT”.

The voltage output is passed to operational amplifier 510, which worksas a low-pass filter to set the voltages across the heating device. Inone embodiment, the heating device is implemented with a power FET 515in combination with a multiplicity of surface mounted resistors 520. Themultiplicity of resistors 520 may be mounted on the PCB substrate in adispersed pattern to provide a given distribution of heat to theelectronic component in the area of the heating device.

In one exemplary embodiment, the resistors 520 may be uniformlydistributed around power FET 515 to provide a uniform distribution ofheat. The uniform distribution of heat enables a constant uniformtemperature over the surface of the PCB substrate directly under theelectronic component. In the case where the electronic component is anoscillator, for example, the constant uniform temperature greatlyimproves the frequency stability of the oscillator in thethermally-stabilized housing.

In another exemplary embodiment, the resistors 520 may be spatiallydistributed around power FET 515 to provide a non-uniform distributionof heat. The non-uniform distribution of heat may be used, for example,to characterize the electronic component. In the case where theelectronic component is an oscillator, the non-uniform distribution ofheat may be used to determine the oscillator's frequency response over awide range of temperatures. This may allow for any unknown oscillator tobe used as the controller together with the thermoelectric devices andtemperature sensors may set up thermal gradients around the oscillatorto understand its response over a wide range of temperatures. Theunknown oscillator may be, for example, an off-the-shelf, inexpensivecomponent that has not yet been characterized.

The foregoing description, for purposes of explanation, used specificnomenclature to provide a thorough understanding of the invention.However, it will be apparent to one skilled in the art that specificdetails are not required in order to practice the invention. Thus, theforegoing descriptions of specific embodiments of the invention arepresented for purposes of illustration and description. They are notintended to be exhaustive or to limit the invention to the precise formsdisclosed; obviously, many modifications and variations are possible inview of the above teachings. The embodiments were chosen and describedin order to best explain the principles of the invention and itspractical applications, they thereby enable others skilled in the art tobest utilize the invention and various embodiments with variousmodifications as are suited to the particular use contemplated. It isintended that the following claims and their equivalents define thescope of the invention.

1. An apparatus comprising: a matrix of thermoelectric devices to setthermal gradients across an electronic component within a housing; amatrix of thermosensitive devices to measure thermal gradientsassociated with the electronic component; and a controller forcontrolling the matrix of thermoelectric devices based on the thermalgradients measured by the matrix of thermosensitive devices, thecontroller configured to identify an average thermal gradient associatedwith an external ambient temperature measured over a given time period,to stabilize temperature within the housing by establishing atemperature set-point above the average thermal gradient, and tomaintain the temperature within the housing at the temperature set-pointso that the temperature within the housing remains above the averagethermal gradient.
 2. The apparatus of claim 1, wherein the electroniccomponent is selected from a surface mounted and a through-hole mountedcomponent mounted on a first surface of a printed circuit boardsubstrate.
 3. The apparatus of claim 2, wherein the housing is mountedon the printed circuit board substrate, and wherein the housing is anenclosed housing.
 4. The apparatus of claim 2, wherein the matrix ofthermoelectric devices includes a plurality of thermoelectric devicesarranged in a two-dimensional grid in a second surface of the substrateopposite the first surface.
 5. The apparatus of claim 4, wherein thematrix of thermosensitive devices includes a plurality ofthermosensitive devices mounted in a two-dimensional grid on the firstsurface of the substrate surrounding the electronic component.
 6. Theapparatus of claim 5, wherein the plurality of thermosensitive devicesare mounted on a surface of the electronic component.
 7. The apparatusof claim 4, wherein the plurality of thermoelectric devices comprises aplurality of heating devices having a plurality of resistive elements.8. The apparatus of claim 4, wherein the plurality of thermoelectricdevices comprises a plurality of Peltier devices.
 9. The apparatus ofclaim 4, further comprising a thermal conducting compound between theelectronic component and the second surface of the substrate.
 10. Theapparatus of claim 1, further comprising an electronic magneticinterference and radio frequency interference shield enclosing theelectronic component.
 11. The apparatus of claim 8, wherein theplurality of thermoelectric devices are arranged to distribute heat tothe electronic component in a thermal dispersion pattern.
 12. Theapparatus of claim 5, wherein the matrix of thermosensitive devicesfurther comprises a thermosensitive device to measure ambienttemperature within the enclosed housing.
 13. The apparatus of claim 1,wherein the electronic component comprises a crystal oscillator.
 14. Theapparatus of claim 1, wherein the controller comprises a multiple-input,multiple-output controller.
 15. The apparatus of claim 1, wherein thecontroller controls the matrix of thermoelectric devices based on amatrix of thermocouple coefficients comprising a plurality ofthermocouple coefficients corresponding to a set of thermal gradientsdetected by the matrix of thermosensitive devices and a set of voltagevalues generated by the matrix of thermoelectric devices.
 16. A methodof controlling thermoelectric devices, comprising: detecting thermalgradients measured by a matrix of thermosensitive devices associatedwith an electronic component within a housing; controlling a set ofcurrent values applied to a matrix of thermoelectric devices based onthe detected thermal gradients; identifying an average thermal gradientassociated with an external ambient temperature measured over a giventime period; and stabilizing temperature within the housing byestablishing a temperature set-point above the average thermal gradient,and by maintaining the temperature within the housing at the temperatureset-point above the average thermal gradient so that the temperaturewithin the housing remains above the average thermal gradient.
 17. Themethod of claim 16, wherein controlling the set of current valuesapplied to the matrix of thermoelectric devices includes controlling aset of current values applied to a plurality of thermoelectric devicesarranged in a two-dimensional grid in a second surface of the substrateopposite the first surface.
 18. The method of claim 16, whereindetecting thermal gradients includes measuring thermal gradients with aplurality of thermosensitive devices mounted in a two-dimensional gridon the first surface of the substrate surrounding the electroniccomponent.
 19. The method of claim 18, wherein detecting thermalgradients includes measuring an ambient temperature outside the housingwith an ambient thermosensitive device.
 20. The method of claim 19,wherein controlling the set of current values applied to the matrix ofthermoelectric devices includes generating a matrix of thermocouplecoefficients comprising a plurality of thermocouple coefficientscorresponding to a set of thermal gradients detected by the matrix ofthermosensitive devices and a set of voltage values generated by thematrix of thermoelectric devices.
 21. The method of claim 20, whereingenerating the matrix of thermocouple coefficients comprises generatingparasitic thermal impedance coefficients for the ambient temperaturemeasured by the ambient thermosensitive device.
 22. The method of claim21, further comprising initializing the matrix of thermocouplecoefficients.
 23. The method of claim 20, wherein generating the matrixof thermocouple coefficients includes adjusting the thermocouplecoefficients based on the temperature set-point.
 24. The method of claim16, wherein identifying the average thermal gradient includes measuringthe average thermal gradient over at least 24 hours.